On October 6, 2020, Jidong County CDC received a report that a family in Sihai Community, Xingnong Town had a suspected foodborne poisoning incident. By the investigation of the county, municipal, and provincial CDC, the incident was due to consumption of the local homemade specialty food, a sour soup, for breakfast on October 5. In the homemade processing and storage, this food was contaminated by Burkholderia gladioli pathovar cocovenenans (B. cocovenenans) which can produce bongkrekic acid (BA), resulting in deaths for all persons exposed due to poisoning. The case attack and fatality rates were both 100% in the persons who consumed the sour soup. Improper processing and storage of fermented corn flour products can cause BA poisoning.
On October 4, a total of 12 persons involving 5 families gathered for lunch and dinner. At around 8∶00 am on October 5, the 12 persons had breakfast together and left separately. Among them, 9 persons consumed the sour soup , while 3 did not and all the 12 persons had consumed the other food items. The 9 persons then successively developed gastrointestinal symptoms such as nausea, vomiting, and abdominal pain. Finally, all 9 cases died after treatment.
On October 6, the investigation revealed that the 9 cases included 4 males and 5 females with an average age of 61 years (range: 45–72 years). Detailed clinical data were collected on the initial patient and her husband. Physical examination of the initial case showed tenderness in the upper abdomen. Laboratory abnormalities include progressive dysfunction of liver function, renal function, and coagulation function in her and her husband, and imaging indicated diffuse changes in the liver (Table 1). The attack rate was 100% in the persons who consumed sour soup and the attack rate was 0% in those who did not consume it, which suggested that the sour soup was the likely source of exposure. The median latency period was estimated as 3 hours (range: 2–8 hours) according to the time of consumption of sour soup and the onset time of the case. The median course of disease in 9 cases was 53 hours (range: 20–341 hours). The patients and cases were numbered 1–9 according to the latency period from short to long (Figure 1). Patient 9 had the longest latency period, and he returned home after receiving prescription medication from the outpatient department. He then died at home with the shortest course of illness, which was only 20 hours.
Patient Gender Age
Latency period (h) Course of disease (h) Clinical manifestation Physical examination Liver function Coagulation function Renal function Imaging Nausea, vomiting Diarrhea Dizziness, fatigue Oliguria Tenderness in the upper abdomen ALT (U/L) AST (U/L) PT
Abdominal CT scan Initial patient’s husband Male 49 4 61 + + + + + 22,640↑ 43,900↑ >120↑ 88.3↑ 30↓ 8.87↑ 466↑ Liver diffuse lesions Initial patient Female 47 2 341 + − + + − 7,199↑ 10,630↑ 71.4↑ 46.6↑ 27↓ 1.84↓ 213↑ Liver diffuse lesions Note: Marks: + : indicates symptoms that do occur; -: indicates symptoms that do not occur; ↑: means increasing; ↓: means decreasing.
Abbreviations and reference ranges: ALT: Alanine aminotransferase 0–40 U/L; AST: Aspartate aminotransferase 0–40 U/L; PLT: Platelets (100–300)*109/L; APTT: Activated partial thromboplastin time 23–35 s; PT: Prothrombin time 10.5–13 s; UREA: Urea nitrogen 2.3–7.2 mmol/L; CREA: Creatinine 44–110 mmol/L
Table 1. The clinical characteristics list of two typical cases in the foodborne bongkrekic acid poisoning incident in Jidong County, Heilongjiang Province, 2020.
Figure 1. Sequence diagram of the course of disease of patients in the foodborne bongkrekic acid poisoning incident in Jidong County, Heilongjiang Province, 2020.
According to the investigation, the process of making the homemade sour soup was as follows: one year ago, the corn was soaked in water for about a month to ferment. After mill grinding, the corn husks were filtered out in the water, and the delicate parts were kept to be dried in flour bags and formed into dough and then noodles with a specialized tool. It was consumed as soon as the noodle-based sour soup was ready and the rest of the dough was put in the refrigerator and frozen. This fall, because the refrigerator was used to store other foods, the dough was made into cornmeal powder and then stored in the refrigerator again to save space. After the corn dough was taken out, it was first exposed to air outside and covered with a simple porous plastic net. After drying for a day, it was transferred to dry in the house due to cloudy and rainy weather.
On October 5, the local public security department extracted all the types of residual food and detected them. No poisonous substances such as cyanide, organophosphorus, carbofuran, psychostimulant, or tetramine were found. On October 7, the municipal CDC tested all the types of food and a patient’s gastrointestinal decompression fluid for salmonella, and the results were negative. The local hospital tested the food and found the aflatoxin was in excess. As this toxin is a common contaminant of corn, and it generally does not cause acute poisoning manifestations as the latency period is usually 2–3 weeks (1), which caused it to be excluded. On October 10, the provincial CDC detected BA in the remaining raw material for the sour soup, the corn flour, and the gastrointestinal decompression fluid. In accordance with national standard (2), the concentration of BA was 330 mg/kg and 3 mg/L, respectively. Combined with the epidemiological investigation result, the patient’s clinical manifestations and laboratory test results, the investigation team confirmed this poisoning incident was caused by BA when bacteria contaminated the corn flour and was used to make the sour soup.